DO MAG-COUPLINGS SLIP? 1

[Ork1]

I am working at a gold mine in Alaska. We have recently installed several mag-couplings on certain pumps which pump processing chemicals, gland water, potable water. They are installed on pumps with vfd's and without. My question is very general in nature; Does the mag-coupling have a certain amount of slippage on the output to the pump or is this "rock solid" technology" and if you know of a reference I could study on these I would appreciate that as well.
Thank You.

 

[moltenmetal]

"Slip" is a difference in rotating speeds, not a minor and limited displacement.

Magnetic couplings which consist of pairs of permanent magnets DO NOT SLIP. They rotate at the same speed until they de-couple.

 

[hydromech]

I think we all know what slip means. Thanks to moltnemetal for clearing that up!!!

So what does de-couple mean? If the flux breaks down between the rotating magnet pairs during transient torque loads, could that not be considered as slip. There would be a speed differential between the two halves of the coupling.

In the context of the original question, where slip is evident. It is safe to assume that the application features a coupling that does have an element of slip. Other applications that have massive permanent magnets and low torque would have no apparent slip.

 

[Ork1]

Please refer to this link. It is a youtube video, it does show how mag-couplings (all with an air gap)
are being used. No pipe strain to worry about, no precision alignments to worry about, less energy to run. But always carry a good strobe light...haha as I have found out.

http://www.youtube.com/watch?v=TtIkYbReMbk

Yes, we are talking about slip and how to accurately work with it.

Thanks all!!!....Scott

 

[ScottyUK]

In the generator world there is a measurement which we know as the load angle. This is a load-dependant angular displacement between driver and driven shaft. Once it reaches 90° the shafts will break out of sync. This angular displacement is not slip. When a synchronous coupling breaks out of lock that condition is what we know as 'pole slipping'. When it occurs on a synchronous machine it is normally very bad news for the machine because of the torque pulsation which occurs.

BigInch,

I'm an analogue guy.


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If we learn from our mistakes I'm getting a great education!

 

[BigInch]

Difference in rotating speeds. I'll remember that.

Scotty, I fear that there's few of you left out there.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[SMOKES]

Permanent mag drives don't slip, They decouple when the torque is exceeded. check if there is any partculate build up in the bottom of the can.Remember the shaft od where the magnet are run a close to inner dimeter of the can.

Reducing the air gap will increase the torque handling of the coupling but.... there is a compromise as the wall of the can sit in the air gap and that has to hold the pressure. so pressure and wall thickness of the can will ditatate the minium air gap.

Is it decoupling at start up use a soft start. If it is decoupling when loaded check the can and bearings for particulate build up. Or use a bigger coupling size.